otel.Tracer(...) concurrent usage

[schmurfy]

Sorry that is not an issue but I cannot find the answer and don't know where to ask: can the tracer object returned by otel.Tracer("xxx") be used in multiple goroutines or should I create it again when I need it ?

I did not found any clear documentation on this and I found conflicting examples where some declare a global variable with the tracer and reuse it and some call otel.Tracer each time they need to create a span.

[MrAlias]

As specified:

Tracer - all methods are safe to be called concurrently.

Also, documented here in this project:

opentelemetry-go/trace/trace.go

Line 671 in 23422c5

// This method must be concurrency safe.

The otel.Tracer function will return either an internal implementation, which is tested here for concurrency safety, or the registered SDK version. If the default SDK, provided by this project, is used it as well is concurrent safe as tested here.

[craigpastro]

👋 A kind of continuation of this discussion I think: If we only plan to use one Tracer in a project, it is better, or perhaps more idiomatic say, to use otel.Tracer(name) where we need access to the tracer, or should the tracer be passed around?

I suppose I am more partial to just calling otel.Tracer(name) where needed as it simplifies my signatures.

Thanks very much!

[dmathieu]

Either works, though calling otel.Tracer will have a performance impact on heavily concurrent applications, as a mutex lock needs to be acquired.
See

opentelemetry-go/sdk/trace/provider.go

Lines 110 to 131 in 23422c5

	func (p *TracerProvider) Tracer(name string, opts ...trace.TracerOption) trace.Tracer {
	c := trace.NewTracerConfig(opts...)
	p.mu.Lock()
	defer p.mu.Unlock()
	if name == "" {
	name = defaultTracerName
	}
	il := instrumentation.Library{
	Name: name,
	Version: c.InstrumentationVersion,
	}
	t, ok := p.namedTracer[il]
	if !ok {
	t = &tracer{
	provider: p,
	instrumentationLibrary: il,
	}
	p.namedTracer[il] = t
	}
	return t
	}

[craigpastro]

Hi @dmathieu ! Ah, that is very helpful to know. Thank you very much!